Insects of Britain and Ireland: the families of Coleoptera

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L. Watson and M. J. Dallwitz

Ptinidae

~Anobiidae-Ptininae.

Spider-beetles.

General appearance. 2–5.5 mm long. Body length/maximum body width 1.45–4.63. Elytral length/pronotal length 1.65–3.2. Base of prothorax not or scarcely narrower than the combined elytral bases, or distinctly narrower than the combined elytral bases. Greatest prothoracic width not narrower or only slightly narrower than the greatest elytral width, or distinctly narrower than greatest elytral width. Beetles oval to elongate; not necked; conspicuously waisted; conspicuously long-legged; brown to black. Upper surfaces of body glabrous or subglabrous, or non-glabrous; exhibiting stiff, erect, dark bristles, or not bristly; with neither scales nor scale-like setae, or exhibiting scales or scale-like setae.

Detailed morphology. Eyes not strongly protuberant; without bristles. The labrum at least partly visible in antero-dorsal view; labrum mostly moderately to heavily sclerotized. Mandibles without a mola; without prosthecae. The mandibular apices simple. The incisor edges of the mandibles simple, or with a single tooth. The maxillae with distinct galea and lacinia apically to the palp, or with a single apical structure additional to the palp. The apical segment of the maxillary palps cylindrical to fusiform. The apical segment of the labial palps more or less expanded apically. Antennae short to long, but not exceeding the insect’s head to tail length; 8–9 segmented, or 11 segmented. Antennal scape not swollen. Antennae filiform. Antennal insertions visible from above.

Cervical sclerites absent. Prothorax shorter than wide. Pronotal length/maximum pronotal width 0.6–1.42. The pronotum without lateral keels. Prothorax at its widest not markedly narrower than the adjoining part of the abdomen. Prothorax without notopleural sutures. Scutellum conspicuous to absent; when pesent, not elevated; anteriorly simple; posteriorly narrowly rounded or acute, or broadly rounded or obtusely angulate, or emarginate. The prosternal process complete; slightly overlapping the mesoventrite to moderately or strongly overlapping the mesoventrite. Metaventrite without a transverse groove. The fore-leg coxae countersunk in ‘procoxal cavities’. The fore-leg coxal cavities open behind externally; broadly open; narrowly separated; slightly transverse, or circular to longer than wide; without lateral extensions; internally closed by a slender bar, or broadly closed internally. The mid-leg coxae countersunk in ‘mesocoxal cavities’; separated by less than the shortest diameter of the cavity, or more than the shortest diameter of the cavity. The mid-leg coxal cavities narrowly separated, or moderately to widely separated; not or scarcely oblique; closed laterally. Hind-leg coxae contiguous or narrowly separated, or widely separated; extending laterally to meet the elytra, or not markedly extended laterally; not shaped posteriorly to receive the femur. Tarsal segmentation formula 5, 5, 5. The tarsi without bilobed segments; without ‘hidden’ segments. Front tarsi with as many segments as the mid-tarsi; 5-segmented. Mid-leg tarsi 5-segmented; pentamerous; the penultimate segment not distinctly shorter than the antepenultimate one. The claws of the mid-leg tarsi not appendaged. The claws of the mid-leg tarsi simple. Hind tarsi with as many segments as the mid-tarsi, or with one segment fewer than the mid-tarsi; 5-segmented (rarely 4?).

Elytral length/maximum width across the elytra 1.03–2.63. Elytra covering most to all of the abdomen; exposing no more than part of the terminal tergite. Elytra with six or more longitudinal lines of punctures, or apunctate, irregularly punctate, or each with fewer than 6 longitudinal lines of punctures or impressed striae; the lines per elytron when more than five, 9, or 10. Scutellary striole present, or absent. Wings well developed, or absent or much reduced. Wings with an anal lobe, or without an anal lobe. Wings without a medial fleck. Abdominal sternites 5; comprising both fused and moveable components. Basal abdominal sternites immovably joined 3. Abdominal segment 8 with apparently functional spiracles, or apparently without functional spiracles. The male external genitalia bostrichoid.

Adult habitat, ecology. Mostly in decaying plant material, or in rotting wood, or in dried plant material, or on shed fur or feathers, or in stored plant products (mainly scavengers in dry plant or animal material); necrophagous, or feeding on dried animal remains, or phytophagous (occasionaly, e.g. Ptinus spp.), or consuming decaying plant material, or eating dried plant material or stored plant products, or consuming rotting wood, or coprophagous.

Larvae. Mature larvae minute (less than 3 mm long), or small to medium-sized. The larvae neither strongly flattened nor disc-like; elongate and more or less parallel-sided; C-shaped in lateral view. Vestiture restricted to fine hairs or setae. The larvae dorsally only very lightly pigmented or sclerotized; ventrally only very lightly pigmented. The antennae 1 segmented. Stemmata absent. The frontoclypeal suture between frons and clypeus distinct. The labrum and head capsule separated by a complete suture. Apices of the mandibles with a single lobe or tooth. The maxillary palps 3 segmented. The labium without ligula between the palps. Labial palps present and segmented; 2 segmented. Mesothoracic legs present and segmented; 5 segmented; with 1 moveable claw. Visible abdominal segments 10. Tergum 9 of the abdomen extending to the underside. The abdomen having functional spiracles on anterior segments (these annular or annular-uniforous); without spiracular tubes. The abdominal apex without a respiratory chamber. Abdominal tergum 8 without amature. The posterior segments without swimming hairs. The last abdominal segment without cerci.

Larvae in decaying plant material, in rotting wood, in dried plant material, in shed fur or feathers, and in stored plant products (mainly in dry plant or animal material; not borers); necrophagous, feeding on dried animal remains, consuming decaying plant material, and eating dried plant material or stored plant products.

The larvae C-shaped, white, setose, hypognathous with small, 2-segmented antennae, the 10 segmented abdomen sometimes with the last two reduced.

Classification. Suborder Polyphaga; Infraorder Bostrichiformia; Superfamily Bostrichoidea.

Representation in Britain and Ireland, and worldwide. About 500 species worldwide; genera 11. 21 species in Britain; genera in Britain 7; Gibbium, Mezium, Ptinus, etc. E.g., Gibbium psylloides (Northern Ptinus); Mezium affine (Shining Ptinus); Ptinus sexpunctatus.

General comments. The antennal insertions close together, separated by less than the length of the scape; the hind coxae without any obvious transverse cavity for reception of the femur..

Illustrations. • Gibbium psylloides (Northern Ptinus: B. Ent. 342). • Gibbium psylloides (details, B. Ent. 342). • Gibbium psylloides: B. Ent. 342, legend+text. • Gibbium psylloides: B. Ent. 342, text cont.. • Mezium affine (Shining Ptinus: B. Ent. 232). • Mezium affine: B. Ent. 232, legend+text. • Mezium affine: B. Ent. 232, text cont.. • Ptinus sexpunctatus: B. Ent. 646. • Ptinus sexpunctatus: B. Ent. 646, legend+text. • Ptinus sexpunctatus: B. Ent. 646, text cont.. • Ptinus (4 spp.), with Cleridae, Drilus and Lymexilidae: Fowler 4, 116 (1890). • Fowler 4, 116 (1890): original legend.. • Gibbium, Ptinus fur, Mezium, Niptus and Tipnus (with Anobiidae): Fowler 4, 117 (1890). • Fowler 4, 117 (1890): original legend.. • Ptinus (3 spp.) and Trigonogenius globulus, with unrelated taxa: Fowler Suppl. 15, 1913. • Fowler Suppl. 15, 1913: original legend.. • Ptinus sexpunctatus (Janson 166).


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Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the families of Coleoptera. Version: 16th May 2016. delta-intkey.com’.

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